Local edge count heuristic for vector interpolator

Abstract

A vector interpolator optimizes the conversion of an interlaced signal to a non-interlaced signal. The vector interpolator improves the visual clarity of slanted features in a displayed image by adjusting the luminance value of each pixel such that the appearance of “steps” or “jaggies” in the features is reduced. For each pixel, the vector interpolator determines a similarity measure for the pixels within a predetermined area around the pixel. From the similarity measure, an angle for interpolation is selected. The luminance value is then interpolated along the selected vector corresponding to the angle and applied to the pixel. One or more ambiguity measures such as a local edge count ambiguity measure may also be computed to indicate the reliability of the computed luminance value.

1. A method for interpolating a value of a pixel, the method comprising:
 generating, using processing circuitry, an ambiguity measure based on frequency content of pixels in an area around the pixel; 
 interpolating a first value of the pixel and a second value of the pixel and computing an estimated value of the pixel based on the ambiguity measure and a weighted sum of the first value and the second value, wherein: 
 a first weight assigned to the first value in the weighted sum is greater than a second weight assigned to the second value in the weighted sum if the ambiguity measure is less than a threshold, and 
 the second weight assigned to the second value is greater than the first weight assigned to the first value otherwise. 
 
     
     
       2. The method of  claim 1 , wherein the ambiguity measure is proportional to the frequency content of the pixels in the area around the pixel. 
     
     
       3. The method of  claim 2 , wherein generating the ambiguity measure comprises:
 computing a mean value for the pixels in the area around the pixel; 
 comparing a value of each pixel in the area around the pixel with the mean value to determine whether each pixel is less than or greater than the mean value; 
 determining a number of times a pixel having a determined value less than the mean value is horizontally adjacent to a pixel having a determined value greater than the mean value; and 
 generating the ambiguity measure to be proportional to the determined number. 
 
     
     
       4. The method of  claim 2 , wherein generating the ambiguity measure comprises evaluating a high pass characteristic of pixels in the area around the pixel. 
     
     
       5. The method of  claim 1 , further comprising:
 determining an angle for interpolation based on a similarity measure for the pixels in the area around the pixel, wherein the first value is based on the determined angle for interpolation. 
 
     
     
       6. The method of  claim 5 , wherein the second value is based on a value of a pixel above the pixel and a value of a pixel below the pixel. 
     
     
       7. The method of  claim 1 , further comprising blending the ambiguity measure with at least one other ambiguity measure to provide an overall ambiguity measure. 
     
     
       8. A system for interpolating a value of a pixel, the system comprising:
 a vector angle estimator operative to generate an ambiguity measure based on frequency content of pixels in an area around the pixel; and 
 an interpolator operative to generate: 
 a first value of the pixel and a second value of the pixel, and 
 an estimated value of the pixel based on the ambiguity measure and a weighted sum of the first value and the second value, wherein: 
 a first weight assigned to the first value in the weighted sum is greater than a second weight assigned to the second value in the weighted sum if the ambiguity measure is less than a threshold, and 
 the second weight assigned to the second value is greater than the first weight assigned to the first value otherwise. 
 
     
     
       9. The system of  claim 8 , wherein the ambiguity measure is proportional to the frequency content of the pixels in the area around the pixel. 
     
     
       10. The system of  claim 9 , wherein the vector angle estimator is further operative to:
 compute a mean value for the pixels in the area around the pixel; 
 compare a value of each pixel in the area around the pixel with the mean value to determine whether each pixel is less than or greater than the mean value; 
 determine a number of times a pixel having a determined value less than the mean value is horizontally adjacent to a pixel having a determined value greater than the mean value; and 
 generate the ambiguity measure to be proportional to the determined number. 
 
     
     
       11. The system of  claim 9 , wherein the vector angle estimator is further operative to evaluate a high pass characteristic of the pixels in the area around the pixel to generate the ambiguity measure. 
     
     
       12. The system of  claim 8 , further comprising:
 a vector angle estimator operative to determine an angle for interpolation based on a similarity measure for pixels in the area around the pixel, wherein the first value is based on the determined angle for interpolation. 
 
     
     
       13. The system of  claim 12 , wherein the second value is based on a value of a pixel above the pixel and a value of a pixel below the pixel. 
     
     
       14. The system of  claim 8 , further comprising circuitry operative to blend the ambiguity measure with at least one other ambiguity measure to provide an overall ambiguity measure. 
     
     
       15. A system for generating an ambiguity measure, the system comprising circuitry operative to:
 compare a determined value of each pixel in a window of pixels with a mean value to determine whether each pixel is less than or greater than the mean value; 
 determine a number of times a pixel having a determined value less than the mean value is horizontally adjacent to a pixel having a determined value greater than the mean value; and 
 generate an ambiguity measure proportional to the determined number, wherein the ambiguity measure is used to produce an estimated value for a pixel being generated. 
 
     
     
       16. The system of  claim 15 , wherein the mean value is an average value of the pixels in a window of pixels surrounding the pixel being generated. 
     
     
       17. The system of  claim 15 , wherein the circuitry is further operative to compare the determined value of each pixel with the mean value by assigning a value of 0 to the pixels having determined values less than the mean value and assigning a value of 1 to pixels having determined values greater than the mean value. 
     
     
       18. The system of  claim 15 , wherein the ambiguity measure is proportional to the number of edges in the window. 
     
     
       19. The system of  claim 15 , wherein the circuitry is further operative to blend a first interpolated value and a second interpolated value to produce the estimated value for the pixel being generated, wherein the first interpolated value and the second interpolated value are blended using the ambiguity measure as a blending factor. 
     
     
       20. The system of  claim 15 , wherein the circuitry is further operative to blend the ambiguity measure with at least one other ambiguity measure to provide an overall ambiguity measure.